Print warning for unused CLI parameters

[marcodelapierre]

In general, I think it is useful to warn users about unused parameters, because they might actually be the result of undesired typos, for instance --resume instead of -resume. In this case, the warning would help them fix the CLI syntax.

Let me talk about both the traditional CLI and CLI v2 (#3600).

I see two main sub-cases so far:

• any non-dash-prefixed argument should give a warning (for CLI v2, also single-dash-prefixed - these would be first checked about -x styled runtime parameters)
• double-dash-prefixed arguments should be compared with a dictionary of params of the pipeline being run; if no match, they should give a warning (for CLI v2, there will be the additional early check around them being runtime parameters)

[aiqc]

Shouldn't it be a hard error? A warning would still allow for kicking off an expensive, time-consuming, and resource-heavy workflow that is being run with incorrect parameters.

For example, I changed params.str in the tutorial to params.greeting to avoid reserved words. However, I forgot to change my command from --str to --greeting.

That's not the result that I wanted. Parameter validation would have prevented this.

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EDIT: It seems like part of the problem is that params can be used throughout the .nf script without first being registered. For example, I don't actually have to define a default value as params.greeting = 'Hello world!' because I can just reference the param directly:

"""
printf '${params.greeting}' | split -b 6 - chunk_
"""

That is to say, parameter validation requires parameter registration.

If this strict-mode functionality were to be introduced, it might have to be enabled in the config in order to avoid breaking changes.

Ideally, it would validate basic types (e.g. str, int, list of str), and maybe predefined values (e.g. params.env:str=['cpu','gpu'] or params.ram:int=range(4:16))

[stale]

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